1. Download a youtube video as mp3 of your desired choosing
here
2. Import the file into your Itunes.
3. Convert the file to aac format in itunes. (Click "File" then "Convert" then "Convert to aac version"
4. Open file location of new file on computer. (Click the new aac version of the song in itunes and choose "show in windows explorer")
5. Set computer to allow file extension changes. (If on windows 10 type "file explorer options" on the taskbar search area then click the "view" tab then uncheck the "hide known extensions" option)
6. change file extension from .aac to .m4r
7. manually drag and drop the new song.m4r file into the ringtones tab of Itunes.
9. Set your itunes to manually manage media for that device and set the ringtones tab to be included.
10. Sync your device.